Erickson Air-Crane Company manufactures a helicopter equipped for aerial fire fighting known as the SK-64 Skycrane Helitanker. See website. A 2,000 gallon tank is fixed to the belly of the helicopter. A fill tube or snorkel extends from the tank and mounts a submersible hydraulic pump at its free end which can be lowered into a body of water for pumping water up the snorkel and into the tank. The snorkel has a 10 inch diameter and a length of about 20 feet or more. About the first 10 feet of the snorkel is required for clearing the landing gear and the remaining length provides clearance between the helicopter and the body of water.
The pump employed is a centrifugal hydraulic pump which is capable of filling the 2,000 gallon tank in less than one minute with a 20 foot lift. The pump weighs about 285 pounds and draws about 20-30 HP of available horsepower from the hydraulic system of the helicopter.
While the Skycrane Helitanker is very effective at fighting ground fires, it has certain disadvantages. The large flow rate and horsepower requirements of the hydraulic pump effectively limit the application of this pumping system to Type 1 (large) military heavy-lift helicopters which have the available hydraulic horsepower to drive the pump. The application of such a hydraulic pump tanker system on smaller military lift helicopters is not known, and understandably so, since they would not have the available hydraulic horsepower capacity needed to drive the pump and would not have the available lift capacity to support the tanker system. The Blackhawk military helicopter, for example, has a lift capacity of about 10,000 pounds.
Another inherent limitation of the Skycrane Helitanker is that is dedicated to lifting and not designed to carry passengers. It would be advantageous to have a firefighting helicopter that, in addition to transporting and spreading water on ground fires, could also transport firefighters to or from the location of the ground fire, particularly while returning with an empty water tank. It would further be desirable to provide a pumping system suited for smaller lift helicopters that would be substantially lighter and would require substantially less horsepower to operate than that of the centrifugal hydraulic pump system of the Skycrane.